1. Field of the Invention
The present invention relates to pistons adapted to convert energy from waves, for example waves in a body of water such as an ocean, lake or river.
2. Description of Related Art
A piston submerged in a body of water may be operated to pressurize a fluid in response to buoyancy forces periodically applied to and removed from a float connected to the distal end of its piston rod by surface waves travelling through the body of water. In this way, some kinetic energy of the incident waves can be converted to potential energy of the pressurized fluid.
However, pistons that have been conventionally adapted for this application suffer from a significant disadvantage: their conversion efficiency declines when incident waves have an amplitude other than an optimal amplitude. At best, a conventional piston may be adapted to have maximum efficiency at the average amplitude for waves in the region where the piston is installed; however, incident waves will have actual amplitudes that occupy a wide range around the average. Furthermore, the average itself is likely to vary over the short term with weather conditions and tides and over the longer term with the seasons and even longer patterns of climate change.
What is needed therefore, is a piston that adapts to the actual amplitude of incident waves so as to improve the efficiency of energy conversion. The present invention is directed to this need.